1. Field of the Invention
The present invention relates to a refrigerating cycle using a mixture refrigerant which is obtained by mixing plural refrigerants having different characteristics.
2. Description of Related Art
In general, a conventional refrigerant circuit of an air conditioner is constructed of a plurality of elements such as a compressor, a condenser, a pressure-reducing device (expansion device), an evaporator and the like, which are connected with each other through a refrigerant tube to form a loop. A gaseous refrigerant of the air conditioner is compressed by the compressor and circulated through the refrigerant circuit. Such gaseous refrigerant thus circulated through the refrigerant circuit is kept to be within a predetermined pressure range. When the gaseous refrigerant is excessively compressed to allow its pressure to go beyond the above predetermined pressure range, the compressor suffers an overload, or the refrigerant circuit is damaged or suffers leakage of the refrigerant around joint portions of the refrigerant circuit. In order to avoid these troubles, various attempts have been hitherto made to prevent the refrigerant from being excessively compressed in the refrigerant circuit.
In the conventional refrigerant circuit, occurrence of excessive pressure of the refrigerant is mostly due to rapid fluctuation in load and an outside air temperature because a flon refrigerant is used in the prior art and it is sensitive to these factors, that is, the factors of inducing the excessive pressure of the refrigerant is mostly based on extrinsic factors. Recently, in order to prevent destruction of a so-called ozone layer, as disclosed in Japanese Patent Laid-Open Patent Application No. Sho-54-2561 for example, there is known an air conditioner using a mixture refrigerant which is prepared from at least two refrigerant components without using any troublesome refrigerant, the refrigerant components being free from chloride and being mixed with each other to provide predetermined refrigerant properties. In this mixture refrigerant, these refrigerant components have different physical characteristics, such as boiling points or condensation pressure. In the air conditioner using such mixture refrigerant, the condensation pressure of the refrigerant in the refrigerant circuit is varied due to change in mixture ratio of the refrigerant components of the mixture refrigerant. Accordingly, in order to keep the air conditioner in a safety condition, it is necessary to keep the mixture ratio of the mixture refrigerant at a fixed value.